Pololu Qik 2s12v10 User manual

Qik 2s12v10 User's Guide
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Contacting Pololu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Connecting the Qik . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.a. Power and Motor Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.b. Logic Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.c. Included Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.d. Jumpers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.e. Indicator LEDs and Phases of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.f. Board Dimensions and Mounting Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4. Serial Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.a. TTL and RS-232 Serial . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.b. Baud Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.c. Command Protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5. Serial Parameters and Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.a. Configuration Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.b. 0x81: Get Firmware Version . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.c. 0x82: Get Error Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.d. 0x83 & 0x84: Get & Set Configuration Parameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.e. 0x86 & 0x87: Motor M0 & M1 Variable Brake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.f. 0x88 – 0x8F: Set Motor Forward/Reverse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.g. 0x90 & 0x91: Get Motor M0 & M1 Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
5.h. 0x92 & 0x93: Get Motor M0 & M1 Speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
6. Cyclic Redundancy Check (CRC) Error Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
6.a. CRC Computation in C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
7. Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Qik 2s12v10 User's Guide © 2001–2009 Pololu Corporation
Page 1 of 30

1. Overview
The qik 2s12v10 adds a comprehensive yet easy-to-use, high-power option to Pololu’s line of motor controllers. The
compact board—it’s almost the same size as the dual VNH2SP30 carrier board [http://www.pololu.com/catalog/product/
708] by itself—allows any microcontroller or computer with a serial port to drive two brushed DC motors with full
direction and speed control, providing up to 13 A (continuous) per motor channel and tolerating peaks as high as
30 A. The improvements over the previous generation and competing products include:
• high-frequency PWM to eliminate switching-induced motor shaft hum or whine
• a robust, high-speed communication protocol with user-configurable error condition response
• visible LEDs and a demo mode to help troubleshoot problematic installations
• reverse power protection on the power supply
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1. Overview Page 2 of 30

Main Features of the Qik 2s12v10
• Simple bidirectional control of two DC brush motors.
• 6 V to 16 V motor supply range.
• 13 A maximum continuous current per motor (30 A peak).
• Logic-level, non-inverted, two-way serial control for easy connection to microcontrollers or robot
controllers.
• RS-232-level, one-way serial control for easy connection to a PC serial port.
• Optional automatic baud rate detection from 1200 bps to 115.2 kbps.
• Seven on-board indicator LEDs (power, status/heartbeat, error indicator, and motor indicators) for debugging
and feedback.
• Error output to make it easier for the main controller to recover from an error condition.
• Jumper-enabled demo mode allowing initial testing without any programming.
• Optional CRC error detection eliminates serial errors caused by noise or software faults.
• Optional motor shutdown on error or serial timeout for additional safety.
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1. Overview Page 3 of 30

Specifications
Motor channels: 2
Motor supply voltage: 6 – 16 V
Continuous output current per channel: 13 A
Peak output current per channel: 30 A
Auto-detect baud rate range: 1200 – 115,200 bps
Available fixed baud rates: 115,200 bps, 38,400 bps, 9600 bps
Available PWM frequencies: 19.7 kHz, 9.8 kHz, 2.5 kHz, 1.2 kHz, 310 Hz, 150 Hz
Reverse voltage protection?: Y
Motor driver: VNH2SP30 x2
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1. Overview Page 4 of 30

Important safety warning
This product is not intended for young children! Younger users should use this product only under adult supervision.
By using this product, you agree not to hold Pololu liable for any injury or damage related to the use or to the
performance of this product. This product is not designed for, and should not be used in, applications where the
malfunction of the product could cause injury or damage. Please take note of these additional precautions:
• This product contains lead, so follow appropriate handling procedures, such as not licking the product and
washing hands after handling.
• Since the PCB and its components are exposed, take standard precautions to protect this product from ESD
(electrostatic discharge), which could damage the on-board electronics. When handing this product to
another person, first touch their hand with your hand to equalize any charge imbalance between you so that
you don’t discharge through the electronics as the exchange is made.
• Review the instructions carefully before making any electrical connections, and do all wiring while the
power is turned off. Incorrect or reversed wiring could cause an electrical short or unpredictable behavior
that damages this product and the devices it is connected to.
• This product is designed to be connected to motors, which should be operated safely. Wear safety glasses,
gloves, or other protective equipment as appropriate, and avoid dangerous situations such as motors spinning
out of control by designing appropriate safeguards and limits into your projects.
Qik 2s12v10 User's Guide © 2001–2009 Pololu Corporation
1. Overview Page 5 of 30

2. Contacting Pololu
You can check the qik 2s12v10 dual serial motor controller page [http://www.pololu.com/catalog/product/1112] for
additional information. We would be delighted to hear from you about any of your projects and about your
experience with the qik motor controller. You can contact us [http://www.pololu.com/contact] directly or post on our
forum [http://forum.pololu.com/]. Tell us what we did well, what we could improve, what you would like to see in the
future, or anything else you would like to say!
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2. Contacting Pololu Page 6 of 30

3. Connecting the Qik
Connecting to the qik can be as simple as hooking up power, your motors, and your serial connections. Many
applications can ignore the jumpers and leave the remaining logic connections unconnected. The qik’s serial
transmit line, TX, is only necessary if you want to get feedback from the controller.
The qik logic and power connections and key components are shown above, and pins are labeled on the back side of
the motor controller. All square pads are ground.
3.a. Power and Motor Connections
Power
The qik motor controller is powered via the large VIN and GND pads on the power side of the board, as shown in
the picture above. The input voltage can be between 6 and 16 V and is the voltage that the motors will see. An
integrated voltage regulator produces the 5 V that powers the board’s logic, so no separate logic power supply is
necessary. Both the input voltage and regulated voltage can be accessed as outputs on the left side of the board (i.e.
the logic connections). See Section 3.b for more information. Please ensure that your power source can supply the
current your motors will draw.
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3. Connecting the Qik Page 7 of 30

Qik 2s12v10 power and motor connections.
Motors
The qik can independently drive up to two bidirectional brushed DC motors, referred to as M0 and M1. The two
terminals of each motor should be connected to the qik as shown above. Variable speed is achieved with 7-bit or
8-bit pulse width modulated (PWM) outputs at one of several selectable frequencies. 7-bit control allows for PWM
frequencies of 19.7 kHz, 2.5 kHz, and 310 Hz; 8-bit control allows for PWM frequencies of 9.8 kHz, 1.2 kHz, and
150 Hz. The highest achievable frequency of 19.7 kHz is ultrasonic, which can result in quieter motor control.
Lower frequencies might produce louder motor noise, but they can help decrease power losses due to switching. The
resolution and frequency can be set via the qik’s PWM configuration parameter (see Section 5.a).
The motor direction convention used in this document is that “forward” corresponds to holding the +output at VIN
while PWMing the -output between ground and high impedance. “Reverse” is the same as forward but with the
outputs flipped: -is held at VIN while +is PWMed between ground and high impedance. As a result, the motor is
rapidly alternating between drive and coast when the direction is “forward” or “reverse”. Variable speed control is
achieved by varying the fraction of the cycle that the motor outputs are driving. Full speed arises when the motor
outputs are driving 100% of the time (one motor output is held at VIN and the other at ground). See Section 5.f for
more information.
The qik 2s12v10 allows for variable braking. In this mode, the motor’s +and -outputs are PWMed between ground
and high impedance. While the outputs are high-impedance, the motor coasts, and while the outputs are tied to
ground the motor brakes. See Section 5.e for more information.
The qik 2s12v10 motor controller uses VNH2SP30 motor driver integrated circuits. These motor drivers have
maximum current ratings of 30 A continuous, but the chips by themselves will overheat at lower currents (see the
table below for typical values). The actual current the qik can deliver will depend on how well the motor drivers are
kept cool. The qik’s printed circuit board is designed to draw heat out of the motor driver chips, but performance can
be improved by adding a heat sink. In our single-driver tests, we were able to deliver 30 A for a fraction of a second
and 20 A for several seconds without overheating the IC. At 6 A, the chip gets just barely noticeably warm to the
touch. For high-current installations, the motor and power supply wires should also be soldered directly instead of
going through the supplied terminal blocks, which are rated for up to 15 A.
• Time to overheat at 30 A: < 1 s
• Time to overheat at 20 A: 35 s
• Time to overheat at 15 A: 150 s
• Time to overheat at ≤ 13 A: N/A (does not overheat)
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Note that these above times were obtained using only one driver with 100% duty cycle at room
temperature without a heat sink. Drawing high currents from both drivers simultaneously could cause
them overheat faster. Switching-induced power losses arising from duty cycles below 100% could also
cause the drivers to overheat faster or lower the continuous current rating.
3.b. Logic Connections
Serial Lines: RX, TX, and SIN
The qik can accept a logic-level (0 – 5 V), non-inverted serial input connected to its serial receive line, RX, and it
can handle baud rates from 1200 – 115,200 bps. This type of serial is often referred to as TTL and is an interface
method commonly used by microcontrollers. The voltage on this pin should not exceed 5 V. The qik provides logic-
level, non-inverted serial output on its serial transmit line, TX, in response to commands that request information.
Information requests always result in the transmission of a single byte per request. If you aren’t interested in
receiving feedback from the qik, you can leave this line disconnected.
The qik can also accept RS-232 serial input connected to the serial receive line, SIN. A computer serial port
typically communicates via RS-232 serial, which is inverted and uses voltages that would be out of spec for the rest
of the qik’s inputs (e.g. -12V to 12V), so SIN is the only pin to which it is safe to make a direct RS-232 connection.
The qik does not have an RS-232 output, so you will need to use an RS-232 level converter connected to the logic-
level output if you need RS-232 feedback from the qik.
Qik 2s12v10 TTL serial connection example (transmit and receive).Qik 2s12v10 RS-232 serial connection example (qik receive only).
Both RX and SIN connect to the same serial port on the qik, so you should not use both of these inputs
simultaneously. Also, don’t forget to connect your serial source’s ground to the qik’s ground!
Reset
The reset line, RST, is an active-low input, which means that it will reset the qik when driven low. This pin is
internally pulled high, so many applications can leave this pin disconnected.
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Error
The error line ERR is an output that is connected to the red error LED and will drive high in response to an error
(which in turn lights the LED). Once an error occurs, the pin outputs high until a serial command is issued to read
the error byte, at which point the pin goes to a high-impedance state that is pulled low through the LED. This allows
you to connect the error lines of multiple qiks to the same digital input. For more information on the possible error
conditions, please see Section 5.c. If you don’t care about error detection, you can leave this pin disconnected.
5V (out)
This line connects to the 5 V output of the qik’s voltage regulator and can be used to power additional electronics in
your system. It can safely supply up to 70 mA beyond what the board draws when VIN is 16 V. The closer the input
voltage is to 5 V, the more current the regulator can deliver without overheating.
VIN (out)
This is a convenient connection point to the input voltage that can be used as a power source for additional
electronics. Note that this pin is not intended to handle high currents, so it should not be used to power the qik
(use the large VIN and GND pads on the other side of the board for this). Do not attempt to draw more than 1 A
from this pin.
Connecting to a 3.3 V Microcontroller
The logic components on the qik 2s12v10 run at 5 V, but it is still possible to interface with a 3.3 V microcontroller.
The RX high input threshold is 3 V, so you can directly connect your microcontroller’s transmit line to the qik’s
TTL serial receive line (i.e. no additional components are required for sending commands to the qik from a 3.3 V
MCU).
If your microcontroller digital inputs are 5V-tolerant, you can make direct connections to the ERR and TX outputs
and RST input, which is weakly pulled to 5 V on the qik. If not, you can leave these optional outputs unconnected,
or you can use external components to decrease the voltage to a range your MCU can handle. A simple way to
accomplish this is by placing voltage dividers between each qik output and your MCU.
3.c. Included Hardware
The qik ships with a 12×1 straight 0.100" male header strip [http://www.pololu.com/catalog/product/965], a 3×2 straight
0.100" male header strip [http://www.pololu.com/catalog/product/966], three 2-pin terminal
blocks [http://www.pololu.com/catalog/product/830], and three red shorting blocks [http://www.pololu.com/catalog/product/971].
For the most compact installation, you can solder wires directly to the qik pins themselves and skip using the
included hardware. For high-current installations, you should avoid using the supplied terminal blocks, which are
rated for up to 15 A, and instead directly solder the motor and power supply wires to the pads.
The included hardware allows you to make less permanent connections. You can break the 12×1 header strip into a
6×1 piece and two 2×1 pieces and solder these strips into the qik’s logic pins where you plan on making
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3. Connecting the Qik Page 10 of 30

connections, or you can use a pair of pliers to pull out the two header pins in the original 12×1 strip for which the
qik has no holes and solder the entire strip to the qik’s logic pins. You can see this latter approach in the picture
below. You can then make your own cables that have female headers [http://www.pololu.com/catalog/category/50] on
them and plug these onto the male headers on your qik, or you can solder the pins to the other side of the board and
simply plug your qik into a breadboard. You might also consider using a 0.100" right-angle male header
strip [http://www.pololu.com/catalog/product/967] (not included) for a lower profile.
The 3×2 header strip can be soldered to the jumper pins as shown above, which lets you make use of the included
shorting blocks, and the included terminal blocks lock together to make a single, 6-pin strip that you can solder to
the power side of the board.
3.d. Jumpers
The qik jumpers allow you to easily alter the behavior of the device. These jumpers can be left off for most
applications. If you use a jumper, it must be in place when the unit first starts up; changing the jumpers while the
unit is running does not take effect until the qik is reset or power is cycled. The only exception to this is the removal
of the demo mode jumper while the qik is in demo mode, which takes the qik out of demo mode.
Fixed-Baud Modes
The jumpers labeled BAUD1 and BAUD2 on the bottom of the qik (i.e. the two closest to the logic connection side
of the board) can be used to set the qik to fixed-baud mode when a shorting block is in place across one or both
jumper locations. When neither of these jumper locations has a shorting block, the qik is in auto-detect mode and
determines the baud rate automatically when it receives the first 0xAA (170 in decimal) byte. If you have a noisy
serial connection or find that the automatic baud detection is not working well for your application, you can use a
shorting block or some other jumper to ground pins BAUD1 and/or BAUD2 (the circular pads right next to the
silkscreen labels). This sets the baud rate to a predetermined value, as described in the table below, and the qik skips
the automatic baud detection phase that normally occurs on start-up.
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BAUD1
Jumper
BAUD2
Jumper Baud Mode
OFF OFF auto-detect baud rate (1200 – 115,200 bps)
ON OFF fixed baud rate at 115,200 bps
OFF ON fixed baud rate at 38,400 bps
ON ON fixed baud rate at 9,600 bps
Enable-CRC Mode
The jumper labeled CRC on the bottom of the qik enables cyclic redundancy check (CRC) mode when the shorting
block is in place. This allows you to increase the robustness of your qik connection through the addition of a CRC
error-checking byte to the end of the command packets you send to the qik. The default behavior of the qik is to
simply respond to a command packet once it receives the last byte. Grounding pin CRC (the circular pad right next
to the “CRC” silkscreen label) causes the qik to expect an additional byte at the end of the command byte that results
from a CRC-7 computation on the entire message. If this byte does not match the expected CRC, the qik ignores the
command and uses the ERR pin to announce a CRC error. Please see Section 6 for more information on how CRC
error detection works. When in this mode, the green heartbeat LED will flicker twice per heartbeat rather than the
single flash that occurs when CRC error checking is disabled.
Demo Mode
If you short pin BAUD1 to pin BAUD2 (the circular pads right next to the silkscreen labels) and reset the qik, it
enters demo mode and remains in demo mode for as long as the short is maintained. Demo mode gives you an easy
way to test your qik and troubleshoot your application for potential problems. In demo mode, the qik smoothly
ramps motor M0 from stopped to full-speed forward to full-speed reverse to stopped again over a few seconds. It
then does the same for motor M1. While motor M0 is active, the red LED is on; while motor M1 is active, the red
LED is off. While a motor is being driven forward, the green LED is on; while a motor is being driven in reverse,
the green LED is off.
Demo mode can help you determine before you’ve even written any code if you have an issue with your power
supply, such as insufficient ability to supply the current your motors are drawing or interference from motor noise.
While in demo mode, any serial data that is received by the qik on the RX line is echoed on the TX line, giving you
an easy way to test your serial connection. It accomplishes this by repeatedly checking the state of the serial input
pin and setting the state of the output pin to match. This process works reliably at low baud rates, but it is not fast
enough to keep up well at higher baud rates, which can result in an echoed byte that does not match the one you
transmitted.
3.e. Indicator LEDs and Phases of Operation
LED Overview
The qik has seven LEDs that are used to provide feedback about its state of operation:
•Power LED (blue): This blue LED is lit when the board is receiving power. It is located on the logic side of
the board.
•Status LED (green): This green LED provides a heartbeat to let you know that your qik is alive and what
state the qik is in, and it also acts as a serial activity indicator. It is is located on the logic side of the board
near the jumpers.
•Error LED (red): This red LED is tied to the ERR output pin and lights in response to an error (which
drives the ERR pin high). Once an error occurs, the LED remains lit until a serial command is issued to read
the error byte, at which point the LED turns off. For more information on the possible error conditions,
please see Section 5.c. It is located on the logic side of the board.
•Motor Indicator LEDs: Each motor has a green and red indicator LED that are tied directly to the motor
driver outputs, for a total of four motor indicator LEDs. The color of the lit LED tells you the direction the
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3. Connecting the Qik Page 12 of 30

motor driver would turn an attached motor (green corresponds to “forward”), and the brightness of the LED
gives you feedback about the speed. Please note that when a motor is attached and driven at an intermediate
speed, it is normal to see both the red and green LED lit simultaneously. This is because the inductance of
the motor keeps the current flowing during the coast phase of the PWM cycle, and since it cannot flow back
through the driver, the only path it has is back through the LED that corresponds to the opposite direction.
These LEDs are located on the power side of the board.
Automatic Baud Detection Phase
When the qik first starts up in automatic baud detection mode, it enters a phase in which it is waiting to receive the
byte 0xAA at a baud rate that is within the range of 1200 bps to 115,200 bps. If the serial receive line RX is pulled
high, as is expected for an idle TTL serial line and the default state of an unconnected RX, the green status LED
fades in and out evenly every 0.8 s. If the serial receive line RX is held low, this is indicative of a bad serial
connection and the red error LED cycles between being on for 0.4 s and off for 0.4 s (and the green status LED is
off).
If a serial byte other than 0xAA is received in this mode, or if 0xAA is transmitted at an invalid baud rate, the red
error LED turns on and stays on until the automatic baud detection phase ends. This gives you feedback that the
baud has not yet successfully been set and you are still in the automatic detection phase. Once the baud is detected,
this phase ends and the qik proceeds to normal operation.
Normal Operation
In normal operation, the green status LED very briefly flashes a heartbeat every 1.3 seconds. If the qik is in enable-
CRC mode, the heartbeat LED flickers twice in rapid succession; if not, it pulses just once per heartbeat. If any
serial activity is detected, the green status LED turns on until the next heartbeat turns it off. If an error occurs, the
red error LED turns on and remains on until you issue a get-error command (see Section 5.c).
Demo Mode
In demo mode, the status and error LEDs cycle through the pattern:
1. red (error) and green (status) on
2. red (error) on and green (status) off
3. red (error) off and green (status) on
4. red (error) and green (status) off
This cycle takes five seconds, and each of the four LED states corresponds to a different output state of the qik’s
motor ports. When the red error LED is on, motor M0 is active, and when the red error LED is off, motor M1 is
active. When the green status LED is on, the active motor is moving forward, and when the green status LED is off,
the active motor is moving in reverse. If you don’t have any motors connected, the motor indicator LEDs light
according to this pattern, and you can see them fade in and out as the motor speed ramps up and back down.
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3. Connecting the Qik Page 13 of 30

3.f. Board Dimensions and Mounting Information
The qik 2s12v10 measures 2.15" x 1.86" x 0.28" (54.6 x 47.2 x 7.1 mm) and weighs 0.5 oz (14 g) without the header
pins or terminal blocks installed. It has four mounting holes, one in each corner. The holes have a diameter of 0.125"
and are designed for #4 or M3 screws.
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3. Connecting the Qik Page 14 of 30

4. Serial Interface
You can use the serial interface for three general purposes: querying the qik for information, setting its configuration
parameters, and sending it motor commands. Motor commands are strictly one-way; all other commands result in
the qik’s responding with a single byte that either represents information that has been requested or feedback on the
effect of the issued command.
4.a. TTL and RS-232 Serial
The qik requires a logic-level (0 to 3.3-5 V, or “TTL”), non-inverted serial input connected to its serial receive line,
RX, or an RS-232 (inverted, ±3-15 V) serial input connected to its SIN pin. The serial interface is asynchronous,
meaning that the sender and receiver each independently time the serial bits; asynchronous serial is available in
computer serial ports (typically RS-232) and as hardware modules called “UARTs” on many microcontrollers
(typically TTL). Asynchronous serial output can also be “bit-banged” by a standard digital output line under
software control.
The data format is 8 data bits, one stop bit, with no parity, which is often expressed as 8-N-1. The diagram below
depicts a typical asynchronous, non-inverted TTL serial byte:
Diagram of a non-inverted TTL serial byte.
A non-inverted TTL serial line has a default (non-active) state of high. A transmitted byte begins with a single low
“start bit”, followed by the bits of the byte, least-significant bit (LSB) first. Logical ones are transmitted as high
(Vcc) and logical zeros are transmitted as low (0 V), which is why this format is referred to as “non-inverted” serial.
The byte is terminated by a “stop bit”, which is the line going high for at least one bit time. Because each byte also
requires start and stop bits, each byte takes 10 bit times to transmit, so the fastest possible data rate in bytes per
second is the baud rate divided by ten. At the maximum baud rate of 115,200 bits per second, the maximum
realizable data rate, with a start bit coming immediately after the preceding byte’s stop bit, is 11,520 bytes per
second.
The voltage on the RX pin should not go below 0 V and should not exceed 5 V. The qik can accept a 3.3 V serial
input on this line, so you can send commands to the qik with a microcontroller running at 3.3 V. The qik provides
logic-level (0 – 5 V) serial output on its serial transmit line TX in response to commands that request information.
Information requests aways result in the transmission of a single byte per request. If you aren’t interested in
receiving feedback from the qik, you can leave this line disconnected.
Note: Only the SIN line is compatible with RS-232 serial, which is inverted and uses voltages that would
be out of spec (e.g. -15 to 15 V). You should not connect RS-232 serial lines to RX or TX. The qik does
not provide RS-232 serial output.
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4.b. Baud Rates
The qik 2s12v10 can handle baud rates between 1200 and 115,200 bps. In its default state, the qik starts up in an
automatic-baud-detection phase and waits to receive the byte 0xAA (decimal 170). The qik detects the baud rate
from this byte and proceeds to the normal operation phase at this baud rate. If you have the one or both of the fixed-
baud jumpers in place, the qik skips the autodetect phase and instead immediately begins normal operation at a baud
rate as indicated in the table below.
BAUD1
Jumper
BAUD2
Jumper Baud Mode
OFF OFF auto-detect baud rate (1200 – 115,200 bps)
ON OFF fixed baud rate at 115,200 bps
OFF ON fixed baud rate at 38,400 bps
ON ON fixed baud rate at 9,600 bps
Please see Section 3.d for more information on the fixed-baud jumpers.
4.c. Command Protocols
Once the qik has entered the normal operation phase, you can control it by issuing serial commands. If your qik is
set to automatically detect the baud, you must first send it the byte 0xAA (170 in decimal) in order to exit autodetect
mode and enter normal operation.
The qik serial command protocol is fairly straightforward. Communication is achieved by sending command packets
consisting of a single command byte followed by any data bytes that command requires. Command bytes always
have their most significant bits set (i.e. they range from 128 – 255, or 0x80 – 0xFF in hex) while data bytes always
have their most significant bits cleared (i.e. they range from 0 – 127, or 0x00 – 0x7F in hex). This means that each
data byte can only transmit seven bits of information.
One significant improvement over earlier Pololu serial controllers is the qik’s error handling, which allows the user
to specify responses to serial errors (which include bad commands, incorrectly formatted commands, or even
hardware-level serial errors), motor fault errors, and motor over-current errors. The qik has a configuration
parameter that determines if the motors shut down when various errors occur, but the qik itself continues running
and accepting commands.
The qik responds to two sub-protocols:
Compact Protocol:
This is the simpler and more compact of the two protocols; it is the protocol you should use if your qik is the only
device connected to your serial line. The qik compact protocol command packet is simply:
command byte (with MSB set), any necessary data bytes
For example, if we want to set motor M1 to full speed forward using the compact protocol, we could send the
following byte sequence:
in hex: 0x8D, 0x7F
in decimal: 141, 127
The byte 0x8D is a command for M1 forward, and the data byte contains the motor speed. Note that every qik
command byte starts with 0x8_ or 0x9_ when using the compact protocol.
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Pololu Protocol:
This protocol is compatible with the serial protocol used by our other serial motor and servo controllers. As such,
you can daisy-chain a qik on a single serial line along with our other serial controllers (including additional qiks)
and, using this protocol, send commands specifically to the desired qik without confusing the other devices on the
line.
The Pololu protocol is to transmit 0xAA (170 in decimal) as the first (command) byte, followed by a device-number
data byte. The default device number for the qik is 10, but this is a configuration parameter you can change. Any qik
on the line whose device number matches the specified device number accepts the command that follows; all other
Pololu devices ignore the command. The remaining bytes in the command packet are the same as the compact
protocol command packet you would send, with one key difference: the compact protocol command byte is now a
data byte for the command 0xAA and hence must have its most significant bit cleared. Therefore, the command
packet is:
0xAA, device # byte, command byte with MSB cleared, any necessary data bytes
For example, if we want to set motor M1 to full speed forward for a qik with device number 10, we could send the
following byte sequence:
in hex: 0xAA, 0x0A, 0x0D, 0x7F
in decimal: 170, 10, 13, 127
Note that 0x0D is the command 0x8D with its most significant bit cleared. Since all compact-protocol command
bytes start with 0x8nor 0x9n, these bytes all turn into data bytes 0x0nor 0x1n, respectively.
The qik responds to both the Pololu and Compact protocols on the fly; you do not need to use a jumper or
configuration parameter to identify which protocol you are using.
Procedure for Daisy-Chaining
Daisy-chaining multiple qiks together on the same serial line is simple. Individually assign each qik a different
device ID using the set configuration parameter command (see Section 5.d), and then connect your TTL serial
transmit line to each qik’s RX line or your RS-232 serial transmit line to each qik’s SIN line. If you wish, you can
connect all of the qiks’ ERR lines to a single input on your controlling module. When you issue your first Pololu-
protocol command, the qiks all automatically detect the baud from the initial 0xAA byte.
Connecting multiple serial outputs to one serial input is more complicated. Each device only transmits when
requested, so if each unit is addressed separately, multiple units will not transmit simultaneously. However, the
outputs are driven, so they cannot simply be wired together. Instead, you can use an AND gate (since the idle state is
high).
If you want to daisy-chain a qik with other Pololu devices that use 0x80 as an initial command byte, the procedure
becomes slightly more complicated. You should first transmit the byte 0x80 so that these devices can automatically
detect the baud rate, and only then should you send the byte 0xAA so that the qik can detect the baud rate. Once all
devices have detected the baud rate, Pololu devices that expect a leading command byte of 0x80 should ignore
command packets that start with 0xAA and qiks will ignore command packets that start with 0x80.
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5. Serial Parameters and Commands
5.a. Configuration Parameters
The qik 2s12v10 has twelve configuration parameters that are saved in non-volatile memory, which means that once
set, these parameters will retain their values even if the unit is powered off. Commands 0x83 and 0x84 are used to
read and write these parameter values, respectively (see Section 5.d). Please note that the memory used to store
these parameters is only rated for approximately 100,000 erase/write cycles, so you should take care not to put set-
parameter commands within loops that are executed many times a second; it is intended that these parameters will
initially be configured as desired and then only changed occasionally. The parameters are numbered as follows:
0: Device ID
default value: 10
allowed values: 0 – 127
This parameter determines which device ID the unit responds to when the Pololu protocol is used. When setting this
parameter, you should only have one qik on your serial line at a time.
1: PWM Parameter
default value: 0 (high-frequency, 7-bit mode—PWM frequency of 19.7 kHz)
allowed values: 0 – 5
This parameter determines resolution and frequency of the pulse width modulation (PWM) signal used to control
motor speed. Note that setting this parameter while the motors are running causes them to stop.
The least-significant bit (bit 0) selects for 7-bit resolution when cleared (i.e. a speed of 127 results in full voltage to
the motors) and 8-bit resolution when set (i.e. a speed of 255 results in full voltage to the motors). A PWM with
7-bit resolution has twice the frequency of one with 8-bit resolution.
Bits 1 and 2 give you additional control over the PWM frequency. When combined with the resolution bit, PWM
parameter can be set to the following six values:
• 0 = 7-bit resolution, high-frequency (PWM frequency of 19.7 kHz, which is ultrasonic)
• 1 = 8-bit resolution, high-frequency (PWM frequency of 9.8 kHz)
• 2 = 7-bit resolution, medium-frequency (PWM frequency of 2.5 kHz)
• 3 = 8-bit resolution, medium-frequency (PWM frequency of 1.2 kHz)
• 4 = 7-bit resolution, low-frequency (PWM frequency of 310 Hz)
• 5 = 8-bit resolution, low-frequency (PWM frequency of 150 Hz)
Using a PWM parameter of zero produces the highest PWM frequency of approximately 20 kHz, which is outside
the range of human hearing and can help make your motors quieter. Using lower frequencies has the benefit of
decreasing power losses due to switching.
2: Shut Down Motors on Error
default value: 1 (stop motors on any serial error)
allowed values: 0 – 7
This parameter controls whether motors M0 and M1 are stopped in response to the various error conditions that can
occur. The three least-significant bits of the parameter let you specify whether the motors are stopped if a serial error
occurs, a motor-over-current error occurs, or a motor-fault error occurs:
• bit 0: if this bit is set, stop motors M0 and M1 when any serial error occurs.
• bit 1: if this bit is set, stop motors M0 and M1 when any motor-over-current error occurs.
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• bit 2: if this bit is set, stop motors M0 and M1 when any motor-fault error occurs.
When this parameter has a value of 7, both motors M0 and M1 are stopped as a safety precaution whenever any
error occurs; conversely, if this parameter has a value of 0, no error causes the motors to stop. For more information
on the various types of errors that can occur, see Section 5.c.
3: Serial Timeout
default value: 0 (serial timeout disabled)
allowed values: 0 – 127
When this parameter has a value of zero, the serial timeout feature is inactive. Otherwise, the value of this parameter
controls how much time can elapse between receptions of valid command packets before a serial timeout error is
generated. This can be used as a general safety feature to allow the qik to identify when communication with the
controlling device is lost and shut down the motors as a result. Note: The shut-down-motors-on-error parameter
must have bit 0—its serial error shut down bit—set for the timeout error to turn off the motors.
The timeout duration is specified in increments of 250 ms (a quarter of a second) and is calculated as the lower four
bits (which are interpreted as a number from 0 – 15) times two to the upper three bits (which are interpreted as a
number from 0 – 7). If the lower four bits are called xand the upper three bits are called y, the equation for the
length of the timeout duration would be:
•timeout = 0.25 seconds * x * 2y= x * 2y-2 seconds
For example, if the timeout parameter is set as 0x5E (01011110 in binary), we have that x= 1110 (binary) = 14
(decimal) and y= 101 (binary) = 5 (decimal), which results in a timeout duration of
• 0.25s * 14 * 25=112 seconds.
The maximum timeout duration (arising from a parameter value of 127) is 8 minutes and the minimum timeout
duration (arising from a parameter value of 1) is 250 ms.
4: Motor M0 Acceleration
5: Motor M1 Acceleration
default value: 0 (controlled speed ramping disabled)
allowed values: 0 – 127
When one of these parameters has a value of zero, acceleration control of the associated motor is inactive.
Otherwise, the M0 and M1 acceleration parameters control the rate at which the the M0 and M1 output voltages are
allowed to increase over time, respectively. These parameters provide a great way to smooth out your motor control
and reduce current spikes caused by sharp increases in motor speed or changes in motor direction.
When acceleration control is active, a set-motor command tells the qik your desired target direction and speed. One
of three cases can then occur:
• If the target speed is lower than the motor speed and the target direction matches the current direction, the
motor speed is immediately set to the target speed.
• If the target speed is higher than the motor speed and the target direction matches the current direction, the
qik linearly ramps the motor speed up to the target speed by adding the value of the associated acceleration
parameter to the speed every 40 ms.
• If the target direction does not match the current direction, the motor speed is immediately set to zero, and
the qik then proceeds to ramp the motor speed linearly from zero to the target speed by adding the value of
the associated acceleration parameter to the speed every 40 ms.
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For example, if the M0 acceleration parameter is 1, it takes a stationary motor M0 5.08 s (127 * 40 ms) to reach a
speed of 127. If the M0 acceleration parameter is 127, it takes a stationary motor M0 40 ms to reach a speed of 127.
The qik actually updates the motor speed 100 times per second, so the speed is really being incremented by a quarter
of the acceleration parameter every 10 ms, which results in even smoother acceleration.
The following oscilloscope captures show qik acceleration in action. When the yellow line is low, the motor driver
is in coast mode, and when the yellow line is high, the motor driver is driving with one output at VIN and the other
at ground. The left capture shows the effect of using an acceleration of 127, and the right capture shows a more
gradual acceleration using a parameter value of 28. The captures were taken with a low PWM frequency (310 Hz) to
make it easier to see the effect of the acceleration on the motor driver output.
Qik 2s12v10 motor driving from speed 0 to 127 with acceleration of
127 and PWM frequency of 310 Hz.
Qik 2s12v10 motor driving from speed 0 to 127 with acceleration of
28 and PWM frequency of 310 Hz.
Please note that acceleration does not apply to braking or to a speed decrease that does not also result in a change of
direction. Motor speed can also be influenced by current-limit settings, which impose additional constraints on the
logic detailed above. Please see the current-limit parameters, which are documented later in this section, for more
information.
6: Motor M0 Brake Duration
7: Motor M1 Brake Duration
default value: 0 (braking on direction change disabled)
allowed values: 0 – 127
When one of these parameters has a value of zero, requested changes of direction for the associated motor occur
immediately. Otherwise, the M0 and M1 brake duration parameters control the amount of time motors M0 and M1
spend braking before the current motor direction is changed from forward to reverse or vice versa. These parameters
provide a great way to smooth out your motor control and reduce current spikes caused by changes in motor
direction.
These parameters represent a time duration in units of 10 ms, so a value of 127 results in a brake duration of 1.27 s.
For example, if the M0 brake duration has a value of 50 and M0 is currently moving forward, issuing an M0-reverse
set-motor command sets motor M0 to full brake for 0.5 s before it acts on the set-motor command.
8: Motor M0 Current Limit / 2
9: Motor M1 Current Limit / 2
default value: 0 (current-limiting disabled)
allowed values: 0 – 127
When one of these parameters has a value of zero, current limiting is inactive for the associated motor. Otherwise,
the current-limiting behavior is determined by the current-limit response parameters (see their parameter description
below for more details). Please note that these parameters specify one half of the desired current limit for each
motor. If you want the current limit to be 16 (which corresponds to 2.4 A), you should set this parameter to 8. The
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